Performance optimization and fouling study of geopolymer-zeolite composite membranes for sustainable textile wastewater treatment

This research introduced a cost-efficient and eco-friendly sustainable geopolymer-zeolite composite membrane produced using a non-hydrothermal technique optimized for treating textile wastewater. A new geopolymer-zeolite composite membrane for microfiltration (macroporosity) was generated by activating metakaolin with sodium hydroxide and silica fume. The design of the experiment methodology (full factorial and response surface methodology) was used to identify the most effective parameters and optimize membrane separation performance. The optimum membrane showed the maximum normalized permeability and turbidity reduction of 0.57 and 97.98%, respectively, at 1.2 bar pressure, 59.6 ^°C feed temperature, and 1.73 L/min. Fouling analysis utilizing resistance-in-series indicated that membrane resistance (57.04%) and cake layer resistance (26.5%) were the primary contributors to overall filtration resistance. Among the four analyzed fouling models (Hermia models), the cake filtration model is the most appropriate for calculating the permeate flux of real wastewater filtration. Removal of the cake layer and backwashing with distilled water effectively regenerated the membrane, restoring over 97.4% of the initial flux and around 99.5% of turbidity reduction across four successive cycles. Scanning electron microscopy (SEM) and elemental mapping validated the structural integrity and cleanability of the membrane, while performance remained consistent across repeated filtration-regeneration cycles. In comparison to traditional ceramic membranes, the engineered geopolymer-zeolite composite exhibited comparable separation efficiency, easy fabrication free of sintering, and significant potential for industrial wastewater recovery applications.